It is well known that vinyl resins may be plasticized, or changed from the hard, horny and stiff state to a soft, plastic workable condition by the addition thereto at elevated temperatures of certain plasticizers, such as dioctyl phthalate, and the like. These vinyl polymers or resins are referred to as the dispersion resins or paste resins and are usually made employing an emulsion polymerization technique, although, in certain instances, a suspension polymerization process can be employed.
When the vinyl resin is mixed or blended with a plasticizer, it is referred to as a "plastisol". By virtue of the flowability of the plastisol it can be processed into various useful products. Plastisol can be used in making molded products, coatings, and the like. Accordingly, the dispersion resin must be capable of being mixed with a plasticizer easily and uniformly to form low viscosity plastisols which are stable, containing particles of uniform and proper size, and capable of producing films, and like products, of good clarity.
In U.S. Pat. No. 4,076,920, issued Feb. 28, 1978, there is described and claimed a process for producing dispersion or paste resins by emulsion polymerization having superior properties for producing plastisols for use in coatings and casting flexible films. These paste resins have improved flow properties and heat stability and the films produced therefrom have excellent clarity and improved water resistance. However, the plastisol foam properties of such resins are not the best and they do not meet the commercial standards of such products as coated fabrics, flooring underlay, foam flooring, and the like. Therefore, there is a need for a paste resin which will meet the criteria for these end uses.
Another detrimental problem in the commercial production of polymers and copolymers of vinyl and vinylidene halides, is the formation of undesirable polymer buildup on the inner surfaces of the reactor. This deposit or buildup of polymer on said reactor surfaces not only interferes with heat transfer, but also decreases productivity and adversely affects polymer quality. Obviously, this polymer buildup must be removed. If not, more buildup occurs rapidly on that already present resulting in a hard, insoluble crust. Accordingly, it is not only desirable to have an emulsion polymerization process in which the plastisol foam properties of the resins are improved, but also in which polymer buildup on the inner surfaces of the reactor is substantially reduced or completely removed.